The objective of this research is to isolate and determine the structure of antineoplastic agents from marine organisms that have confirmed activity in the National Cancer Institute's in vivo (PS) and/or in vitro (KB, P388 L1210) test systems. Isolation will be guided by activity testing provided by the National Cancer Institute. Some compounds having interesting levels of cytotoxicity will be isolated in larger quantity for in vivo antitumor testing. Certain cytotoxic compounds will be modified to check for improved in vitro and in vivo activity. Attempts will be made to identify the likely microbial source of highly cytotoxic polyether antibiotic type compounds. A variety of well-established separation techniques will be used to isolate compounds and structures will be determined by single crystal x-ray analysis and/or other spectroscopic methods. The structures of structurally novel compounds obtained incidental to the primary objective will be investigated to the extent possible. The long term goal is to discover clinically useful anticancer agents.